Comparing direct charge injection and Forster energy transfer into quantum dots in hybrid organic/inorganic quantum dot light emitting devices

Abstract

White light-emitting devices based on the combined emission from red CdSe/ZnS quantum dots, green phosphorescent, and blue fluorescent organic molecules Inorganic quantum dots (QDs) have excellent optoelectronic properties. But, due in part to a lack of a suitable medium for dispersion, they have not been extensively used in optoelectronic devices. With the advent of organic semiconductors, the integration of quantum dots into optoelectronic devices has become possible. Such devices are termed as hybrid organic/inorganic quantum dot light emitting devices. In hybrid organic/inorganic quantum dot light emitting devices, the mechanisms of charge and/or energy transfer into the quantum dots include Forster energy transfer and direct charge injection. Forster energy transfer involves formation of excitons on organic semiconductors, followed by an energy transfer onto the inorganic quantum dots, where the exciton recombines resulting in emission of a photon. Direct charge injection is the mechanism in which the electrons and holes are directly injected into the quantum dots and they recombine on the quantum dots to result in a photon. Which mechanism is operating in a device has been a subject of contention. In this work, by using various device configurations, we show that both these mechanisms can operate independently to maximize the quantum dot light emission in such devices.

Modeling charge transport in quantum dot light emitting devices with NiO and ZnO transport layers and Si quantum dots

“…Colloidal quantum dots (QDs) are well suited for display technologies because of their tunable band gap and hence wavelength tunable luminescence properties. [1][2][3][4] Optimization and other development efforts potentially can be minimized for different colored light emitting diodes (LEDs) because essentially the same structure may be used to create LEDs of various colors. If appropriately chosen, electron and hole transport layers and their contacts need not be varied.…”

7.4: Invited Paper: High‐Efficiency Inverted Quantum‐dot Light Emitting Diodes for Display

“…Such as energy level alignment and decrease of charge injection barrier can be evaluated by studying electron and hole only devices. [23].…”

Excitation of Thin Cyanine Films via Energy Transfer from Si Substrate

“…On the other hand, energy transfer has been studied as a possible method for exciting the colloidal quantum dots covered by organic insulators [18][19][20][21][22][23] : several studies regarding the energy transfer between organic and inorganic materials have been carried out. [24][25][26][27][28] The energy transfer is nonradiatively caused by the overlap between the absorption spectrum of the energy acceptor and the luminescence spectrum of the energy donor without any direct contact. Therefore, if energy transfer from a semiconductor substrate to an organic molecule film can be induced, electroluminescent devices could be realized wherein the aforementioned energy matching is not required.…”